i want to set up a circuit which senses electric signals of the body (electro-cardio signals) and sends them to an iphone mic jack. I have already downloaded and hooked up a circuit to detect heartbeats (you can see the circuit diagram at the following link, I am excluding 'http' otherwise the website will not accept the message): //sites.google.com/site/hearts09site/home/technical-setup), i get a reasonably reliable signal of amplitude approx. +/- 4V ( I have yet to check the exact value with a multi-meter), so what I would like you to comment on is: 1. can there be an even better circuit (smaller/cheaper to hook-up) 2. the setup/modification required to input this signal into the mic jack of the iphone I may mention that this is in connection with a project i am working on as part of my masters degree (in Sydney), and would be glad to acknowledge your contribution. I need to finalise this electronics part of the design ASAP, so if possible then you can please message me directly on my gmail address as well (maksdesk at gmail.com). Thnx in advance and regards.